So what a relief to rediscover Volumetrics, a way of eating that just plain makes sense. By pumping up your diet's volume in easy ways (more of that to come), you will not only enjoy yummy foods, but also eat a lot of them and still lose weight.

It all comes down to calories per bite. "By choosing foods that have fewer calories per bite, your portion size grows, but your overall calorie count decreases," explains Barbara Rolls, PhD, the creator of Volumetrics and author of the new book The Ultimate Volumetrics Diet. "So you end up with a satisfying amount of food."

Key word: satisfying. Rolls, a professor of nutritional sciences at the Pennsylvania State University, has spent 20 years studying the science of satietythat feeling of fullness at the end of a mealand how it affects hunger and obesity. Research shows that the amount of food we eat has a greater effect on how full we feel than the number of calories in the food. If you're sated after eating, you're likelier to stick with a diet. The staples of the Volumetrics planwater-rich foods like brothy soups, fruits and vegetables, whole grains, low-fat dairy, lean meat, and fishnot only help control hunger by filling you up, but they also do it on fewer calories. Foods that are high in fat and/or sugar are just the opposite: They're less filling, plus they have more calories per bite.

So the trick is to limit the low-volume foods and eat mostly high-volume ones. Doing so allows you to double, sometimes triple, your portions and still lose weight, says Rolls. But "volumizing" your meals isn't simply about piling veggies next to a serving of lasagna or throwing extra tomato slices or lettuce leaves on your cheeseburger. It's also about packing your recipes with low-density ingredients.

In a study co-authored by Rolls and published in a 2011 issue of the American Journal of Clinical Nutrition, people who ate an entree made up of 25% pureed vegetablesin this case, squash and cauliflower were blended into macaroni and cheeseconsumed 360 fewer calories per "volumize" the dish, tricking your brain into thinking you're eating more when in fact you're eating less.

Pumping up foods with air also works to increase volume and promote satiety. For example, instead of munching on a handful of potato chips, you can fill up on three handfuls of air-popped popcorn for the same number of calories. The benefit of that sort of smart swap became apparent during one of Rolls' studies (ultimately published in 2007 in the journal Appetite). She and her team of researchers served Cheetos to two groups of women. One group got the original Crunchy Cheetos and the other group was given the airy version, Cheetos Puffs. Because the snacks differed in aeration and, therefore, volume, the Puffs group ended up taking in 73% more food, but 21% fewer calories.

Next Page: Volumetics rules for you to follow [ pagebreak ]Curious to see how you can pump up your meals and sleek up in the process? Here are Rolls' rules for putting this science to work for you.

Add fruits and vegetables to everythingVolumizing sounds time consumingall that choppingbut it doesn't have to be. Rolls suggests multitasking: Do veggie prep while you catch up with your kids or partner. In a pinch, buy them ready-to-go. "Markets sell fresh vegetables already washed, peeled, and chopped," says Rolls. "Frozen veggies are a good alternative in cooked dishes, and many come already chopped."

Recipes to Drop 5 Pounds in One WeekFollow this 1,400-calorie-a-day plan for seven days (include moderate exercise) to drop up to 5 pounds. Read moreYour Eat-More Diet Plan

Eat before you eatYou read that right. Fill up on a low-cal soup or way, you'll get a head start on your goal (to stave off hunger pangs). But again, make it easy: Buy ready-to-go bags of salad greens, and stock up on the fixings for a quick soupreduced sodium broth, frozen veggiesor buy good-for-you, broth-based ones that are ready-made.

Satisfy your eyes firstThe goal is a full plate. Why? Before you even take a bite, you subconsciously take in that sight and your brain registers satisfaction. Realizing you won't be leaving the table hungry makes you less likely to eat too much of the wrong foods, explains Rolls. To create a bountiful plate without adding calories, include ingredients that add water or extra air such as mousse-style yogurt and puffed rice cereal.

Dont forget proteinIt's key to satiety, but you can eat half a day's worth of calories if you don't choose wisely. Opt for small portions of low-fat protein, whether it's skim milk on your cereal, beans on your salad, tofu with dinner, or lean cuts of beef, chicken, or fish.

Clean your plate (no, really)Since the goal is to feel full at the end of each meal, this is practically required. "Other diets ask you to eat less, but we see that as a half-empty plate," says Rolls. Not to mention a half-empty stomach.